Acoustical treatment structure



Aug.1,1967l T.MAR|NER 3,333,524. AcousTIcAL TREATMENT, STRUCTURE Filed Dec. SO, 1964 2 Sheets-SheetV 2 INVENTOR THOMAS MARINER BY Mw r ATORNEY United States Patent O M 3,333,524 ACOUSTICAL TREATMENT STRUCTURE Thomas Mariner, Mount `Foy, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Penn- Sylvania Filed Dec. 30, 1964, Ser. No. 422,159 7 Claims. (Cl. 98-40) This invention relates to acoustical treatment of building construction particularly in cases where a subceiling is supported below the main ceiling of a room and where partitions extending from the floor of the room to the subceiling are used to partition the space in the room into a plurality of somewhat segregated areas. Many problems have been encountered with this type of construction with regard to the transmission of sound and noise from one area upwardly through the ceiling, through the space between the subceiling and the main ceiling, and nally, downwardly through the subceiling into the area on the side of the partition opposite to that side from which the sound or noise originated. These problems acquired added significance in those ceiling systems wherein the subceiling was formed of perforate acoustical panels through which conditioned air which was supplied to the space above the subceiling was distributed to the room area or areas beneath said acoustical subceiling. In such cases, sound waves may pass through the perforate areas in the panels, thus reducing the transmission loss of the panels and the attenuation factor of the ceiling.

One solution to the problem was to place additional acoustical material in the space between the subceiling and the main ceiling so that the sound which found its way into said space would be absorbed therein by this material without being transmitted to the areas below said subceiling. This particular solution proved to be quite costl'y in installation and restricted the ow and distribution of air above the subceiling to varying degrees.

An object of the present invention'is `to provide sound blocking means in a space between Ventilating, acoustical wall means and another wall means lof a building construction wherein said sound blocking means cooperate with at least one partition wall means exterior of said space to.

substantially reduce the transmission of sound in said space and between adjacent areas separated by said partition wall means.

Other objects of the present invention will be apparent from the detailed description below with reference to the drawings wherein FIGURE l is a view in perspective of a building construction embodying an acoustical treatment structure according to the present invention;

FIGURE 2 is a view in perspective of a building construction embodying a modified form of the structure of the present invention;

FIGURE 3 is an enlarged, sectional view of a modied form of structural joint which may be used with either of the embodiments shown in FIGURES 1 and 2; and

FIGURE 4 is an enlarged, partial view in section of an acoustical panel.

Referring now to FIGURE 1, there is shown a building structure having an upper wall or ceiling 21, a lower wall or floor 22, and side walls 23 which extend around the periphery of a building structure 20 to enclose the space 24 between the ceiling 21 and the oor 22. The space 24 is separated into smaller areas by partition walls 25 which may extend from the floor 22 to the Vceiling 21.. Each partition wall 25 has a plurality of apertures 26 extending therethrough in its upper portion.

An acoustical ceiling 27 is suspended below the main ceiling 21 in each area of space 24 between the various partition walls 25. The acoustical ceiling coinprises support runners 28 which are suspended by hanger wires 29 3,333,524 Patented Aug. 1, 1967 ICC from the main ceiling 21. Support angles 30 are secured to the Various partition walls 25 and side walls 23. Acoustical panels 31 extend between the various runners and support angles to provide acoustical treatment for the area in which they are located.

At least some of the panels 31 are of the acoustical Ventilating type which contain air distributing apertures 32 therethrough as is known in the art. An air supply duct 33 communicates with the space above the panels 31 and supplies air thereto in a known manner. The air which is supplied to the space above the panels 31 is free to pass through the apertures 26 in the partition walls 25. The air so supplied is at a pressure slightly greater than that of the air in the areas below the panels 31. It will be apparent that the air above the panels will distribute itself throughout the spa-ce thereabove until suflicient pressure is built up to force the air downwardly through the apertures 32 in the panels 31 to the spaces thereunder. Thus, the space above the acoustical panels 31 operates as a plenum, and the air supplied thereto will be uniformly distributed through the panels 31 to the areas therebeneath as is known in the art. Principles of Ventilating ceilings may be found in an article entitled Plenum Engineering-A Key to Success With Ventilating Ceilings by Dr. T. Mariner in Heating, Piping, and Air Conditioning magazine, October 1962, pages -140.

The apertures 26 in partition walls 25 are sized and located to accommodate the air flow required to permit adequate distribution between the various Iareas above panels 31. It is apparent that the greatest attenuation will be obtained with those partitions having the least amount of open area therethrough. Thus, the air flow area afforded by a particular partition preferably should be no greater that that required for adequate air distribution in order to obtain the highest possible sound attenuation.

The apertures 26 in partition wall 25 preferably are located as close to the main ceilingv21 as is possible. This arrangement of the apertures 26 substantially restricts the transmission of noise and sound from an area below the panels 31 on one side of a partition wall 25 through the partition 26 in the space above panels 31 to the area below the panels 31 on another side of said partition 26. Further, the apertures 26 in partition walls 25 will allow the air to be distributed evenly throughout the space above the panels 31 while performing their sound attenuating function. This arrangement represents a substantial Iadvance over the prior art in reducing the transmission of sound from one side of a partition upwardly through the acoustical ceiling thereabove, over the partition, and downwardly through the acoustical ceiling on the opposite side of the partition into the Iroom therebelow, it being understood that the prior art partitions extended only to the acoustical ceiling without extending substantially into the plenum space thereabove.

Referring now to FIGURE 2, there is shown a partial view in perspective of a building construction having an upper wall or ceiling 3,4 and side wall 35. The space be-' neath ceiling 34 is separated into smaller areas by means of partitions 36 which may extend upwardly from the lioor of the area underlying ceiling 34 which floor is not shown. The partitions 36 terminate a short distance below ceiling 34. T-shaped support runners 37 are suspended by wire hangers 38 from ceiling 34. Support angles 39 are secured to partitions 36. Acoustical panels 40 extend between various support runners and channels. The acoustical panels 40 are similar to panels 31 mentioned above and yat least some of which are of the Ventilating type having perforations 41 therethrough to allow air to pass from one side of said panel to the other.

Inlet 42 in wall 35 is connected to a source of air which may be conditioned according to the requirements of the 4 areas to be used. Air is supplied through inlet 42 to the space between ceiling 34 and acoustical panels 4f). This space operates as a plenum and is filled with the air from inlet 42 which air is under a pressure slightly greater than that of the air in the areas below the acoustical panels 4f) whereupon the air in the plenum will pass through said panels 40 and will be uniformly distributed to each partitioned area. The extent of the partitions 36 above the panels 4f) perform the same function attributed to the similar portions of partition 25 described heretofore in that they operate as sound barriers between adjacent areas on either side of a particular partition in the space above panels 40. Thus, any sound which passes through the panels 4f) in a particular area must travel the distance to the top of any particular partition wall 36 in order to pass thereover into an adjacent plenum space and subsequently through the panels 40 therein into the area therebelow. As in the case of the structure shown in FIGURE l, the principles of Ventilating ceilings found in the magazine article are applicable to the structure shown in FIGURE 2. Similarly, the air ow area between a particular partition and the main ceiling in FIGURE 2 preferably should be no greater than that required for adequate air distribution in order to obtain the highest possible sound attenuation. As a practical matter, economics of 4construction will usually dictate that an imperforate plenum partition should have an effective height which is at least about one-third and preferably one-half of the height of the plenum with which it is associated. Although measurable attenuation is afforded by plenum partitions having heights less than those specified, it usually will not be enough to justify the expense of the partition and its installation.

As stated heretofore, principles for design of ventilating ceilings are presented in Plenum Engineering-A Key to Success With Ventilating Ceilings, Heating, Piping, and Air Conditioning, October 1962, pages 130- 140, where it is shown how to design a Ventilating ceiling installation which Will provide a predetermined degree of uniformity of plenum pressure. One of the significant results of the design process is the specification of a minimum plenum height. Often the actual plenum height will be chosen larger than the minimum plenum height because of general architectural considerations, and the variation of plenum pressure will be much less than that considered as an objective maximum in the design.

Whether :a large plenum height is dictated by the prin ciples of design of Ventilating ceilings, or by general architectural considerations, the use of a large plenum height generally accentuates the transmission of sound from room to room through the ceiling, or in other words gives a lower attenuation factor than that obtained with smaller plenum height, as has been shown in an article entitled Theory of Sound Transmission Through Suspended Ceilings Over Partitions, by Dr. T. Mariner in Noise Control magazine, vol. 5, No. 6, pages 13-18, Novembber 1959. Although the subject of this invention is applicable for all plenum heights, it is particularly needed for larger plenum heights and is also particularly effective for the large plenum heights.

One method of designing the partition means according to this invention would be to rst make an arbitrary decision concerning how large a pressure drop will be permitted to occur between the plenum space into which the air is introduced and the plenum space between the terminal end of the plenum and the last such partition means. Then, taking into account the number `of such intervening partition means, the known plenum pressure, the known plenum height, and the known distance between the partition and the terminal end of the plenum, the formulas and other information in the Plenum Engineering article may be used if the partition means are treated as a class of obstruction, in order to determine the effective obstruction or partition height and corresponding minimum permitted clearance (difference between plenum height and eifetive obstruction height) corresponding to the arbitrarily selected additional pressure drop. Then the ratio 10X logarithm of the plenum height over the clearance defines the maximum obtainable improvement in attenuation factor approximately. One may, of course, elect to use larger clearances and accept a correspondingly reduced improvement in attenuation factor.

It is to be understood that the term effective height as used herein is the same as that defined in the Plenum Engineering article. For example, if a solid partition spans the full width of the plenum, then the effective height is equal to the actual height of the partition. If the partition contains open areas and/or it does not span the entire plenum width, the effective height thereof is equal to the actual imperforate area of the partition divided by the width of the plenum. Thus, the formulas and information in the above noted article may be used to determine specific requirements for various types of plenum sound barriers or partitions according to the present invention including the embodiments shown and described herein.

It is, of course, clear from well known acoustical principles that the improvements in attenuation factor attributable to a plenum partition will be obtained only if the material of which the plenum partition is made has a transmission loss several decibels greater than the desired improvement in attenuation factor.

Using the aforementioned principles, if it is desired to consider a plenum above a Ventilating ceiling which overlies five offices in 4a row, each l0 feet long in the direction of air flow in the plenum, a design air flow rate of 2 c.f.m./sq. ft. of ceiling and a plenum height of 2 feet may be specied. In order to minimize air pressure variations in the common plenum above all of the offices, the supply duct stub should be located over the center office. Assuming that a maximum of 10% additional variation of plenum pressure is desired and that all of the ceiling tiles o-r panels are of the Ventilating type, the formulas and information in the Plenum Engineering article may be used to determine that an effective plenum barrier or partition height of 20.5 inches and an effective clearance of 3.5 inches should be used. The frequency aver-age improvement of attenuation factor in this case will be 8.3 decibels approximately.

In the example directly above, if only 25% of the ceiling tiles or panels are of the Ventilating type, the effective barrier or partition height would be 22.3 inches and the effective clearance would be 1.7 inches. In this case, the average improvement in attenuation factor will be 11.5 decibels.

Referring now to FIGURE 3, there is shown an enlarged, partial, sectional View of a joint between a sectional or discontin-uous partition wall. The lower partition section 43 supports a support member 44 having two pairs of opposed channels. Channel 45 receives the upper end of partition section 43. Channel portion 46 receives the lower end of upper partition section 47. Opposed channels 48 and 49 receive opposed ends of acoustical panels 50 and 51. This type of joint structure and discontinuous partition wall may be used with either of the embodiments shown in FIGURES l and 2. It is to be understood that the type and shape of support member is not critical and may be varied. Two or more sections may be used in any particular partition.

It is to be understood that the partitions may take any shape or form and may be comprised of any of the well known building materials. The material or materials and `dimensions including thickness or thicknesses of any particular partition may be varied. For example, one material of a given thickness may be used for a portion of a partition in the plenum while a different material of the same or different thickness may be used for another portion of the partition which s located inside or outside the plenum. As mentioned heretofore, the particular height or heights or open areas of the partitions within the plenum area to afford the proper amount of air -ilow area over, through, or around a particular partition may be determined by the principles of air llow, plenum,

and acoustical engineering as set forth in the examples and publication described above. The partition height and/or open area afforded by any particular partition may be varied and may be dilerent from that height and/ or open area of other partitions in the same plenum or building. The shape and/or location of each open area may be varied and need not be the same in any particular partition, plenum or building. The partitions or portions thereof in the plenum may be inclined to the ceiling with which they are associated at angles other than 90. It is apparent that many dilferent types of partitions including dilerent embodiments of the present invention may be used in the same plenum space to cooperate with the partitions outside said space to allow uniform air distribution while substantially reducing the transmission of sound between adjacent areas.

It is to be understood that the air which is supplied to the plenum may be conditioned in a conventional manner as described in the publications set forth above and i-s well known in the art. Suitable provision for exhausting the individual areas to which ail is supplied may be provided as is Well known in the art. Some of the exhaust air may be recirculated if desired.

It is to be understood that the term wall as used herein is deemed to include not only side walls but floors, ceilings, partitions, etc., and that the structure of the present invention may be utilized in any such Wall structure.

It is apparent that the structure of the present invention in the disclosed embodiments provides for effective acoustical zoning and privacy through increased sound attenuation between partitioned areas under a ventilating, acoustical ceiling without substantially interfering with uniform air distribution to said areas.

Various modifications will be apparent to those skilled in the art without departing from the spirit and scope of the invention as defined in the claims.

I claim:

1. A building construction comprising a subceiling to be spaced below a main ceiling of a room, said subceiling including acoustical panel means, means to support said panel means and means to allow air to pass through said panel means, partition means extending above and below said subceiling, said partition means extending above said subceiling to :a point at least about one-third of the vertical distance between said subceiling and said main ceiling, means to supply :air -above said subceiling whereby said Iair will Ibe free to pass through said subceiling to points therebelow on all sides of said partition means, said partition means above the subceiling is positioned so that -air ow is not obstructed but whereby noise which -may pass from below said subceiling on one side of said partition means upwardly through said subceiling would be substantially obstructed from passing t-o another side of said partition means and thereafter downwardly through said subceiling.

2. A building construction according to claim 1 wherein said partition means extend upwardly at least about one-half of the vertical distance between said :subceiling and said main ceiling and wherein said partition means are substantially planar.

3. A building construction acording to claim 1 wherein said partition means are continuous.

4. A building construction .according to claim 1 wherein said partition means extend upwardly to said main ceiling and :said partition means include perforate portions to allow air to pass therethrough.

5. A building construction according to claim 1 wherein said partition means are discontinuous.

6; A building construction according to claim S Wherein said partition means lare discontinuous and include at least two sections, one of which extends from a side of said subceiling upwardly and another section of which extends below said subceiling.

7. A building construction comprising a subceiling to be spaced below a main ceiling of a room, said subceiling including acoustical panel means, means to support said panel means and means to allow air to pass through said panel means, partition means extending bel-ow and above said subceiling, means to supply air above said subceiling, said partition means being so constructed and arranged to have an elective height to permit the free flow of air above the subceiling and through the subceiling on all sides of the partition means, but to obstruct the passing of noise upward through the subceiling, past the partition and downward through the subceiling on the other side of the partition means.

References Cited UNITED STATES PATENTS 209,342 10/18718 Hawley 918-32 2,291,220 7/1942 Germonprez 98-40 2,058,411 10/1962 Hanson et al. 98-40 3,082,487 3/1963 Fowler et al.

MEYER PERLIN, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

1. A BUILDING CONSTRUCTION COMPRISING A SUBCEILING TO BE SPACED BELOW A MAIN CEILING OF A ROOM, SAID SUBCEILING INCLUDING ACOUSTICAL PANEL MEANS, MEANS TO SUPPORT SAID PANEL MEANS AND MEANS TO ALLOW AIR TO PASS THROUGH SAID PANEL MEANS, PARTITION MEANS EXTENDING ABOVE AND BELOW SAID SUBCEILING, SAID PARTITION MEANS EXTENDING ABOVE SAID SUBCEILING TO A POINT AT LEAST ABOUT ONE-THIRD OF THE VERTICAL DISTANCE BETWEEN SAID SUBCEILING AND SAID MAIN CEILING, MEANS TO SUPPLY AIR ABOVE SAID SUBCEILING WHEREBY SAID AIR WILL BE FREE TO PASS THROUGH SAID SUBCEILING TO POINTS THEREBELOW ON ALL SIDES OF SAID PARTITION MEANS, SAID PARTITION MEANS ABOVE THE SUBCEILING IS POSITIONED SO THAT AIR FLOW IS NOT OBSTRUCTED BUT WHEREBY NOISE WHICH MAY PASS FROM BELOW SAID SUBCEILING ON ONE SIDE OF SAID PARTITION MEANS UPWARDLY THROUGH SAID SUBCEILING WOULD BE SUBSTANTIALLY OBSTRUCTED FROM PASSING TO ANOTHER SIDE OF SAID PARTITION MEANS AND THEREAFTER DOWNWARDLY THROUGH SAID SUBCEILING. 